Salam,
Brother I am very new here. I don't possess enough knowledge to provide you with a satisfying answer.
But to my little knowledge, what I have understood is the whole of mankind isn't necessarily the best creation of God almighty.
Rather, God has called men who do not use their reason, or who are bent on denying the truth as the vilest/worst of of all creatures (8:22, 98:6)
But those 'who believe and do righteous deeds', i.e. live their lives in God's way are the best of all creatures (98:7).
So it appears to me that only the believing men and women, who believe and do righteous deeds are perhaps the best of all creatures. But those who keep denying the truth despite clear evidence having come to them are the worst of all.
May God forgive me if my answer is erroneous.